Method and means for engraving the dies of lenticular optical selectors



Aug. 30, 1949. M. BONNET 2,430,354

. METHOD AND MEANS FOR ENGRAVING THE DIES OF LENTICULAR OPTICAL SELECTORS Filed Dec. 1, 1945 5 Shets-Sheet 1 Aug. 30, 1949.

M. BONNET 2,430,354

METHOD AND MEANS FOR ENGRAVING THE DIES OF LENTICULAR OPTICAL SELECTORS Filed Dec. 1, 1945 I 3 Sheets-Sheet 2 1949- M. BONNET 2,480,354

METHOD AND MEANS FOR ENGRAVING THE DIES OF LENTICULAR OPTICAL SELECTORS Fil ed Dec. 1, 1945 5 Sheets-Sheet 3 Patented Aug. 30, 1949 METHOD AND MEANS FOR ENGRAVING THE DIES OF LENTICULAR- OPTICAL SELECTORS Maurice Bonnet, Paris, France, assignor to La Reliephographie, Societe pour lExploitation des Procedes de Photographic en Relief Maurice Bonnet, Paris, France, a corporation of France Application Deccmbcr l, 1945, Serial No. 632,184 In France December 1, 1944 7 Claims.

The present invention relates to the manufacture of optical selector nets having cylindrical or spherical lenticular elements. It permits a considerable extension of their possibilities of use, and at the same time assures a very high degree of optical perfection.

a lenticular element formed from a die engraved according to the prior art.

Fig. 2 is a similar View of a lenticular element formed from a die engraved according to the present invention.

Fig, 3 is a diagrammatic fragmentary cross sectional View of a tool in the process of removing a chip from a die.

Fig. 4 is a diagrammatic fragmentary perspective view of the tool in the process of removing a chip from a die. I

Fig, 5 is a fragmentary perspective View of one type of cutting tool forming part of the present invention.

Fig. 6 is a plan view of a matrix partially engraved by the tool of Fig, 5.

Fig. '7 is a perspective view of the matrix of .Fig 6 in more complete form.

. radii, with the tool represented in Fig. 5.

The invention is similar to the processes in the third category referred to, that is to say those in which a tool with a cutting edge is used, generally constituted bya diamond. It consists essentially in effecting the engraving operation by removing the chippings in the transverse direction to the rectilinear-grooves corresponding to the lenses of nets having cylindrical refractive elements.

According to the invention and contrary to the processes hitherto known, the dimensions of the diamond itself do not enter into consideration, the radius of curvature of the grooves no longer depends on the amplitude of the arcuate path impressed on the cutting tool, about an axis parallel to the grooves to be formed. Thus selecting netshaving lenses of very different dimensions varying for example between.la. .of, a m./m. and a centimetre in width can be obtained with dies engraved by: means of the same tool and the same machine. 'Now, the possibility of easily providing selector nets of Very different optical characteristics allows one to envisage multiple optical combinations of conjugate nets of which the practical applications are very extensive,

Further, the fact itself that the tool is displaced in an arc of a circle around a rotating axis, assures the obtaining of a groove with a perfectly circular profile, which it is practically impossible to obtain by using a moulding tool of which the curve cannot be geometrically perfeet.

According to another characteristic of the invention, it is moreover possible to guide the tool in such manner as to describe a path conforming exactly with any profile whatsoever of a die of large dimensions, a profile which it is easy to obtain with a very great precision, having regard precisely to the dimensions of this die.

The best diamond tools which the specialist industry is able to provide did not have-and could not have, in the present state of the artan absolute degree of perfection. In reality, Whatever the care given to their cutting, the edge of these diamonds is not ideal; it has microscopical splinters of the order of the size of a micron, and of which in addition the number rapidly increases as soon as the tool starts to work.

The influence of these imperceptible splinters is quite negligible in current practice. Applicant has, however, sought to determine what would be their effect on the optical efficiency of selectors having lenticular elements.

The results of these researches will be shown below, with the help of Figures 1 and 2 of the accompanying drawings, which show respectively, on a very enlarged scale and without regard to proportions, two cylindrical lenticular elements of optical selector nets, one made by the present cause any transverse diffusion.

methods, the other in accordance with the invention.

In these two figures, an accidental scratch d is shown fresultin'g frorn a splinter on the cutting edge of the tool which 'was used to engrave the die for these screens, while a designates one of the cylindrical lenses of the selector net, I) a light sensitive plate placed in front of this lens, and c the support for this plate.

It is known, in peri-stereoscopic photography, for example, that the object of each of the lenses of the view-finder or selectograph is to give rise to an infinite number of image lines such as 'e in the sensitised plate, the lines being extremely fine and close together, and the width of which is of the order of one hundredth of a millimeter. Thus, in the cross section representedbyli igure 1, the lens a normally gives rise to the image point I, for example.

The effectof the scratch d is to diffuse into 't'heinserie'r'ei the lens a the parasitic rays, which are liable to cover the sensitized plate along a iine'g ,1theiehgfih or which can be equal to the total width 'of the lens a Furthermore, these rays which can themselves encroach upon the part of :the sensitised plate corresponding to neighbouring lenses.

I -It appears clear that this covering action, to the extent it 'is liable'to happen in practice, tends to "e'oh'iue'e the image lines which should remain In so doing, 'it will directly efifect the :might'distort the peri-s'tereoscopic image, or give rise to troublesome secondary images.

In Figure 2, on the 'contr'a'ry, the vertical image line created by thelensa, is for example the line The transverse scratch dealised eventually by a splin te'r in the cutting tool, is found, for example, in th e horizontal plan of the lens which corresponds to the image point j appertaining to the image line It is found ithat this transverse scratch dbnl'y causes difiusive action in the vertical direction, in spreading the point f along the image line ejfor the distanceg-h for example. The "difierent image lines therefore alwaysremain distinct since the scratch (1 cannot n d I In reality, its radius of curvature is obviously the same as that of the lens ugproper. No distortion is therefore caused in the peri-stereoscopic effectand no secondary image is apparent to the observer, at the a'n e m s f e ima edisappear can obviously be envisaged only inthe longitudinal direction of the grooves, it would therefore be unsuitable for abolishing the longitudinal scratches of the latteryon the contrary,

this same-polishing actionwou-ld-allow the easy elimination of transverse scratches. Thus, the described process would .havenot only for effect, as has justbeen shown, the elimination of the influence :of the scratchesif .it exists in the grooves, but it affords moreover the means of abolishing them. In these circumstances, the qualities of thesurface of the selector nets formed according to the invention approaches perfection.

The tool destined to putinto practice the method according to the invention introduces original sible in order to give the maximum resistance to the tool, is only limited by the exigencies of disengaging the tool in the course of the work. It is seen in effect in Figure 3 that the disengaging face must avoid the piece of work, when this tool is at the end of its operative stroke having finished I its oscillating movement around the axis X'Y parallel to its cutting edge and passing into the plane of the attacking 'face A of thetool. I

Always with a'view to'obtaining a cutting edge as resistant as possible, "the extremity of the dihedral formed by the tool is truncated by a face'tdf small width, forming with the attacking surface A an 'angle at as near 'as possible to 90 and only reduced to the extent necessary in practice for dismantling the tool,

The mounting of "the'diamon'd which in'general constitutes the tool, "must, also, satisfy the exigencies of disengagement in relation to the 5 piece of work, thus according to the invention,

the part of this mounting, which coincides with the disengaging face Dco'nstituted the prolongation of the said face.

Preferably, thefeng'raving operation by the 0 method whichis 'thesuhjectbfthe invention is preceded by roughenin'g down strokes with the aid of at'ool, of Known type, removing the chip in the longitudinal direction'oji the groove. Figure 4 showshow the groovesG 'andG rough- 5 ene'd dbwn stillperrhit finelo'ngitudirial scratches of the type "of those "represented by Figure 1.

In the groove G3, on the-contrary, in \vhich'the cutting has been finished in accordance "with the methodwllichisthe-subjectof the invention, the

5 scratches in question are directed transversely of the'groo'v'eand'corresponding 'to'that in Figure 2.

In the foregoing, there has been noquestion of the execution of rectilirie'ar cylindrical'grooves,

in the material which -constitutesthe die (metal for example).

The present invention affords moreover the 'means "of engravi'ng the [dies intended for the production 'of'selectbr netshavin'g spherical lenses (so calledpitted selector nets).

It 'is sufiicient fo'r this'purpose, as shown in Figure 5, tofuse a tooloffthe "sa'me'type as'that described-above, biitof "which'the cutting edge, instead'ofbein'grectilinear forms an arc of a 5 circle of which the radius R, is "equal tothat 0f the arcof acircle describ ed'by the medial point P of the said edge,iarbund the axis X-'Y. At each strokejthe tool removes-e chipof curved cross sectionQinSt'ad of detaching 'a're'cta'ngular chip,

and, in eohsequehee, "hollows out spherical cells in thedie, presenting, 'fore'xample, the aspect shown in Fig'ufeB.

I If one increasesthe depth'of penetration of the tool linto the .metalfithe :cells present the I aspect indicated in perspective in Figure 7. This last arrangement ensures to the screen the best efiiciency, since thewhole of it's surface contributes to the'refraction of luminous rays, contrary to that of the zones Z which remain level in the case ofFigureG. I I

According to the invention cells ofdifferent radii can be hollowed out with the aid of the same tool with a circular cutting edge, makin the tool turn round on its vertical axis in such manner as to make it attack the cell obliquely (see Figure 12). The trace of this edge in the metal worked would then be an arc of an ellipse corresponding to the small radius of the latter.

In these circumstances, itwill suffice lto regulate the radius of oscillation of the edge of the tool to renderit equal to the small radius of the ellipse, with a view to forming'in the die substantially spherical cells of smaller radius than that of the edge of the tool.

Figures 11 and 12 illustrate this means. In Figure 1l,the groove cut with the aid of a tool such as that shown in Figure 5, of which the edge, which is an arc of a circle shown in plan, penetrates the metal according to the width L, possesses a radius of curvature equal to that of the said edge. It is easily understood that the radius of curvature of the groove will be more reduced if the same tool attacks the groove obliquely as indicatedin Figure 12.

A complete engraving machine, allowing the putting into practice of the method according to the invention, using the tool shown in Figures 3 and 4', and adapted to the making of rectilinear grooves with a cylindricalprofile, is shown diagrammatically in Figure 8 by way of example. In this figure the different members occupy arbitrary positions in order to increase the clarity of the drawin'g'and to make very evident the interaction of the saidmembers.

In the bearings I a shaft 2 for holding thework turns, the end of which carries a lead screw 3 engaged in a nut 4, supported by one of the bearings. On the shaft 2 a cylindricalwork supporting cylinder 5 is fixed, around which is wrapped and secured byany ,desired means, the sheet 6, for example, of copper, which it is proposed to engrave in order to make the castingdie.

The tool support I, disposed perpendicularly t the axis of the shaft 2, constitutes a' bearing in which turns a sleeve: 8 :having an eccentric bore. The sleeve 8 carries an arm9 held against an adjustable abutment by a spring III. The end of the arm 9 carries a roller I2 on which rolls a cam I3, keyed to an operating shaft I4. This shaft I4 also carries an arm I5 to which is pivoted one of the ends of a link I6 of which the other end is pivotedto another arm IT. This arm I! is keyed on one of the ends of a shaft I8, guided in the eccentric bore of the sleeve 8 and at the other end of which is fixed aslide I9 on which a member can be displaced radially, and in which the cutting tool 2| is mounted, suitably adjustable in the said member 20. I

The shaft I4 through the intermediary of two bevel pinions 22, '23 rotates with a main operating shaft 24 the bearings of which are not represented, and which carries two eccentric rings 25 on which are mounted two arms 26 and 2'! bearing at their free end a pawl bar 28. Thisbar the length of which corresponds tothe travel of the cylindrical work supporter 5, engages with the teeth of a ratchet wheel 29, keyed to the shaft 2. The shaft 24 further carries two other eccentric rings 30 on which are mounted two arms 3|, 32, connected bya cross bar 33 forming a balance 6 weight. The eccentricities of the rings 25 and 30 are opposite and the weight of the assembly3l, 32, 33 is calculated to balance the assembly 26, 21, 28. The operation of this arrangement is as followsz "The shaft 24 is started up, the pawl bar 28, at each revolution engages anew tooth of the ratchet wheel 29 and thus causes discontinuous rotation of the shaft 2 and the screw 3. At each displace ment of the bar 28 there is an equal and corresponding displacement in an inverse direction of the'balance weight 33, owing to which a perfect balance of the rocking assembly is obtained. Because of the action of the screw 3 engaged in the nut t, the shaft 2, and consequently the piece of work 6 moves in a spiral path in front of the tool 25 with a discontinuous movement.

Since the shaft l4 turns at the same speed as the shaft 24, the arm I! performs a double swing for each revolution of the shaft 24. The oscillation of the crank I! in the direction indicated by the arrow corresponds to the movement of the removing of a chip by the tool 2|. After each operative stroke the tool must be disengaged from the piece of work to return rearwardly. This disengagement is caused by the rotation of the sleeve 8 under the action of the cam. I3 which at each revolution, acts upon the lever 9 while the tool swings towards the back round the axis X-Y. When the sleeve 8 turns, this axis XY moves in a suitable direction around the axis VW of the sleeve.

The depth of cut of the tool edge is adjusted by the abutment II. Thus the roller I2 and the cam I3 separate during the operative stroke of the tool 2I, to the benefitof greater precision in the execution of the stroke for removing the chip.

The adjustment of the tool in relation to the piece of work or, in other words, the adjustment of the amount by which the cutting edge of the tool extends beyond the axis of oscillation X-Y of the latter is easily obtained by altering the position of the member 20 in the slide I9, locking members being, it is understood, provided in order to immobilise the tool after adjustment.

It must be noted that this tool, according to the invention, swings round a non-material axis X-Y, which permits the giving of very small values to the'radius of oscillation of the cutting edge, which it would be impossible to obtain if the tool was mounted directly on a fixed pivot, constituting the axis X-Y. The radii of oscillation to be envisaged for the cutting edge must be in reality of millimetre order, even of millimetre. The arrangement shown allows considerably reduced radii to be readily obtained while assuring the tool a very precise guidance in the sleeve 3 of the shaft I8 which can both be of large diameter. In all cases the arc of the circle generated is perfect.

The adjustment of the penetration of the tool into the metal of the die will be notably facilitated by an optical system permitting a source of light placed behind the diamond, and projecting to a greatly magnified extent, the silhouette of the cutting edge and that of the bottom of the orifice upon a screen perpendicular to the said edge. The same light arrangement will also permit the determining with great precision of the radius of oscillation of the. cutting edge round its non-material axis of rotation. The machine being in motion, the end of the diamond will form a concaveimpression on the projection screen, if its edge is placed on this sideof the.

7 axis of oscillation anda convex image if the tool passes the said axis. It will remain fixed, if it coincides exactly with the axis."

Figure 9 shows a modification of th machine represented in Figure 8,'permitting the obtainingof grooves of Whichthe profile is elliptical, fo'r'example, insta'dof presenting a'c'ircmar sectionas mthe machine first described: figare only indicates the members of the machine concerned in" this modification; consists substantially'in reproducing at the cutting edge of the'tooljby the intermediary'of apanto'graph arrangement, the path-imposed on a guiding member displaced-relatively to a die having the selected profile.

Figurelo shows the geometrical outline of the practical form shown in Figure '9.-

The arm ll"is"here"--again"made to swing at each revolution by the li'rik'lfi, but this arm-l1 carries'inaddition a pivot 34 on which'is pivoted one-of-the ends of an arm 35, of which the other endpivotsat -35" on another arm 3'1, parallel to the plane'passing through the axisof the pivot 3fi and through the axis X Y'. The arm 31 piv ots at 38 'on' the arm't 'andit ends in a rol1er39 which rolls on'aninterchangeable cam 40; The total length of the arm 35in'cluding the roller 39 is-equal to the-distance which separates the point 38 from the axis V-'--W of the sleeve 8. I

The Figure shows thearrangement of the jointed parallelogram thus-realised; The length D-"of the arm 31 is-chosen in proportion to the radius d of the arc of the circle described by the cuttirigedg'of the tool around the axis XY, in such'manner asto realize the relation The radius of oscillation d and the attacking edge being adjustable beforehand, the side D must itself also be of variable length, so as to constantly assure the similarityof the above triangles. To this end, and as Figure 9 shows, the roller 39' is movably mounted upon the arm 31', by the intermediary of a slide 4|, and the cam w'is itself movably mounted in the direction iridicated by the arrows, in such manner as to allowthe modification of the distance whichseparates it from'the point 38, in proportion to the variation of lengthimposed on the radius d by the changing of position ofthe member 20 upon the slide I9.

A spring A2 maintains the roller 3!? constantly against the cam'dil, the cam l3 acts upon the arm 9 against this spring. The cam 40 consequently plays the same role as the abutment H in the preceding figure.

Figure 10 clearly shows how, owingto thi parallelogram arrangement just described, any deformation imposed upon triangle' V3938 will be transmitted to the similar triangle VX'C. When the pivot24' rocking to and fro round the centre V; under the impulse of the link It, the sides D and d pivot at an equalangle, around the two fixed pivots 38 andX.- Onthe other hand, in the course of its stroke against the cam 40, the roller 39 gives to the pivot 38 an oscillating movement around the axis V, the movement in proportion to the coordinated rectangular vertical of the curveof the cam. The movement is transmitted to'the piv'ot'a' and to the side 11,- In sum, the edge C'follows a path Whichco'rresponds to the curve-of the cam '40 the ratio of the armsof thel'ver D, d ends, a.

It 'wilfeasilybe appreciated'that the technical progress realised, owing to the invr'ition, which permits the establishment of a uriiversal machine capable-of providing dies for casting selector nets whether they have cylindrical lenses of whatsoever radius of curvaturewhether they liave"spherical lenses -of whatsoever radius of eurvatureyorwhethr they have cylindrical lenses of whatsoever corrected'profile, (elliptical, para belie, hyperholid'etc) the same tool with a diamend ofr'ectilmear edge ca'nbe used 'for the making of cylindrical grooves, and the same tool with afie'dgetliat it is an arc of a circle for all spheriear reoves;

Having" now particularly described and ascertained"the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

p 1. A"mach ine tool for cutting circular grooves in a cylindrical surface, particularly applicable to'engraving the dies for molding lenticular optical selector nets, such as those used in peristereoscopic photography, including in combinatibn a fixed nut member, a Work-supporting shaft terminating in a lead screw engaging said nut member; a cylinder for carrying the sheet on which the engraving is to be effected, said cylinder being secured to said'shaft, a tool holder disposed perpendicular to the axis of said shaft, an eccentric sleeve mounted in said tool holder, at tool-carrying shaft guided insaid sleeve, means forrocking said sleeve, a lever fixed to said sleeve, acam controlling said lever, to effect disengagement-of the tool, an abutment'for said lever, saidabutment determinin with precision the position of engagement of the tool, an actuating mechanism including a ratchet device for effecting discontinuous rotation-of said work-supporting shaft, anda commoncontrol mechanism for synchronizing the movements of the above recited integers.

2. 'A machine tool according to claim 1, wherein the ratchet device includes a toothed wheel, fast on-tl'iework-supporting shaft, a pawl bar having K said toothed wheel.

3.'Amachine for cutting circular grooves ina cylindrical surface} particularly applicable to engraving' the dies for molding lenticular optical sel'ector nets, suchas those used in peristereo= sco'pic photography, includin in combination an oscillatably: mounted tool holder, means for mounting a; to'ol iri said tool'l'iolder with itscutting edge in close proximity to the axis about which the holde'r oscillates; and parallel to said axis; and means for rocking said tool holder, wherebythe cutting'edg of the tool describes a patlfon an arc of'a cii'cle about said axis of oscillation, which is perpendicular to the axis ofthe cylindrical surface to be engraved, said tool having an attacliing surface and a. disengaging surface disposed at an angle corresponding totheangle through'which the tool is oscillated soasto-avoid contact of the disengaging surface with the cylindricalsui'facetti be engraved at'the end'bf' thecutting stroke o'f'the tool, the axis about which the tool oscillates being parallel to the cutting edge and in the plane of the attacking face of the tool, and a, mounting for said cutting tool, forming a plane extension of its disengagement face.

4. A machine for cutting circular grooves in a cylindrical surface, particularly applicable to engraving the dies for molding lenticular optical selector nets, such as those used in peristereoscopic photography, including in combination an oscillatably mounted tool holder, mean for mounting a tool in said tool holder with its cutting edge in close proximity to the axis about which the holder oscillates, and parallel to said axis, and means for rocking said tool holder, whereby the cutting edge of the tool describes a path on an arc of a circle about said axis of oscillation, which is perpendicular to the axis of the cylindrical surface to be engraved, said tool having an attaching surface and a disengaging surface disposed at an angle corresponding to the angle through which the tool is oscillated so as to avoid contact of the disengaging surface with the cylindrical surface to be engraved at the end of the cutting stroke of the tool, the axis about which the tool oscillates' being parallel to the cutting edge and in the plane of the attacking face of the tool, and a tool holder including in combination an oscillatable head forming a stirrup, having two branches, of which one branch is parallel to the axis of oscillation, and means for adjusting said last mentioned branch longitudinally of the other branch, to permit variation of the radius of the circular are described by the cutting edge of the tool.

5. A machine for cutting circular holes in a cylindrical surface, particularly applicable to engraving dies for molding lenticular optical selector nets, such as those used in peristereoscopic photography, and more especially applicable to the obtaining of selecting nets having spherical lenticular elements, including in combination an oscillatably mounted, tool holder, means for mounting a tool in said tool holder with its cutting edge in the neighborhood of the axis about which the holder oscillates, and parallel to said axis, and means for rocking said tool holder, whereby the cutting edge of the tool describes a path on an arc of a circle about said axis of oscillation, which is perpendicular to the axis of the cylindrical surface to be engraved, the cutting edge of the tool forming an arc of a circle, to

produce a part-spherical cell, at each operative stroke of the tool, the radius of curvature of the cutting edge of the tool being equal to the radius of the arc of the circle described by the median point of the said edge about the axis of oscillagraving dies for molding lentlcular optical selector nets, such as those used in peristereoscopic photography, and more especially applicable to the obtaining of selecting nets having spherical lenticular elements, including in combination an oscillatably mounted tool holder, means for mounting a tool in said tool holder, with its cutting edge in the neighborhood of the axis about which the holder oscillates, and parallel to said axis, means for rocking said tool holder, whereby the cutting edge of the tool describes a path on an arc of a circle about said axis of oscillation, which is perpendicular to the axis of the cylindrical surface to be engraved, the cutting edge of the tool forming an arc of a circle, to produce a part-spherical cell, at each operative stroke of the tool, the tool being adjustable by rotation in its mounting, in order to permit the use of the same tool, having an edge in the form of a circular arc, for cutting cells of different radii.

7. A method of engraving dies for molding lenticular optical selector nets, such as those used in peristereoscopic photography for example, by forming circular grooves in a cylindrical surface of a work piece and permitting the removal of machining scratches extending perpendicularl to the axes of the grooves to be engraved, comprising removing successive chips in a direction trans.. versely of a groove to be engraved by oscillating a cutting tool about an axis parallel to the groove to be engraved and located externally relatively to the cylindrical surface, disengaging the tool from the surface after each cuttin stroke, holding the work piece stationary during each cutting stroke and advancing the work piece during the return stroke of the tool while the tool is disengaged from the surface.

MAURICE BONNET.

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